Many innovative technologies have been developed in the recent telecommunications revolution, the most important of which undoubtedly include the creation of the Internet and the development of wireless communication systems. The Internet and other IP-based networks have enabled virtually instantaneous communication between millions of individuals across the globe. Wireless communication systems, and wireless mobile systems in particular, have allowed individuals to communicate while roaming over large distances in otherwise inaccessible regions, thereby making traditional home telephone service and wireline communication networks virtually obsolete in many situations.
The combination of the Internet and wireless communication technologies has resulted in the development of a number of popular products that enjoy both the accessability of the Internet and the convenience and mobility of wireless communication systems. It is not uncommon for typical cellular customers to use their cellular phone to connect to the Internet, surf the web, communicate with others using e-mail, upload and download news, files and information, and perform virtually every other Internet operation previously limited to personal computer users connected to the Internet via wireline systems. Such cellular phones and other similar wireless devices allow individuals to access the Internet when communicating through wireless IP-based networks, thereby providing tremendous convenience, power and flexibility.
Although the combination of the Internet and wireless communication technologies has been largely successful, there nonetheless remain some difficulties and problems associated with the merger of these previously independent technologies. In particular, the ability to assign and validate IP addresses remains a difficult problem for wireless network systems that employ Internet Protocol and similar IP-based protocols to communicate information.
Internet Protocol operates based on the assignment of a unique IP address to each individual network attachment point. An IP address represents both the identification and location of a particular terminal. Information is communicated between different users by specifying the information content, source IP address of the information sender, and destination IP address of the information recipient. The information content is then sent from the sender to the recipient based on the source and destination IP addresses specified with the information content. The address of the recipient is determined simply by examining the destination IP address, and the recipient is able to determine who the sender is and reply to the sender by examining the source IP address.
Although information is sent from the sender to the recipient, the information is rarely sent directly from the sender to the recipient. Instead, the information undergoes a process called routing, wherein the information is sent to a number of intermediate locations. A router at the intermediate location examines the source and destination IP addresses included with the information content to determine the next appropriate location to which to send the information. The information content itself is usually subdivided into smaller information pieces known as packets, and each packet includes its own source and destination IP address. Thus, each individual packet may be routed along distinct and independent routes to proceed from the sender to the recipient.
In order to send and receive information, each individual terminal must have an IP address. When a terminal connects to an IP network, it may often need to dynamically obtain an IP address. Dynamic IP address assignment, as well as general IP address management, occurs through dynamic IP address assignment protocols. For instance, the Dynamic Host Configuration Protocol (DHCP) and other similar protocols include a dynamic IP address assignment protocol that controls IP address allocation, including the assignment, distribution, maintenance and release of IP addresses for network hosts within an IP network.
When dynamic IP address assignment occurs under a protocol such as DHCP, the terminal requests an IP address from the IP network, and an IP address server within the IP network assigns the terminal an IP address from the pool of unassigned IP addresses that are available to the IP network. The user communicates with the IP network throughout the user's network session by using the assigned IP address. When the terminal disconnects from the IP network, the terminal releases this IP address, thereby making the IP address available for the IP network to assign to a new terminal. In this fashion, the IP network is able to reassign the same IP address to different users that connect to the IP network at different times.
In order for the terminal to cause an IP address server to assign an IP address to the terminal for use throughout a user's network session, the user broadcasts an IP address assignment request (assignment request) to a portion of the IP network, using a predetermined broadcast IP address as the destination IP address for the assignment request. This broadcast IP address is recognized by the IP network when routing the assignment request sent by the user. The broadcast of the assignment request sends the assignment request to all network hosts connected to the IP network, including all other users and IP address servers connected to that portion of the IP network. A major shortcoming of broadcasting address requests, address validation requests, and responses to these requests to every mobile is that they cause the mobiles to consume their power unnecessarily. Power on a mobile terminal is a scarce resource and should not be wasted unnecessarily.
As mentioned above, the IP address for each terminal in an IP network represents both the address and the location of that terminal within the IP network. In particular, individual users may be attached to different subnets of an IP network, which are simply smaller portions of an IP network. For each subnet, only certain IP addresses are valid for receiving IP packets from the subnet, because an IP address represents both location and identity. As a result, a user who is assigned an IP address is limited to only those subnets for which their IP address is valid.
When a terminal broadcasts an assignment request in a system where the IP network is divided into subnets, an IP address server within the terminal's subnet serves the assignment request, and the IP address server assigns the terminal an IP address that is valid within the terminal's current subnet. In this fashion, when an IP network is divided into subnets, an assignment request is not broadcast to the entire IP network, but is instead broadcast only within the terminal's particular subnet.
Traditionally, users in IP networks have been connected to an IP network via fixed or wireline connections, and therefore have not been able to migrate from one IP subnet to another. Thus, although a user's IP address represents the user's location or subnet within an IP network and limits the user to that location or subnet, this limitation traditionally has had little effect on IP-based communications. For instance, wireline and non-mobile Internet users are unable to migrate out of their particular subnet once they connect to an IP network; therefore, the user's IP address remains valid throughout their network session, and the user broadcasts only one assignment request and no validation requests per network session. With the advent of wireless IP networks, however, users are now able to migrate from one subnet to another, and this mobility significantly decreases the performance and efficiency of wireless IP networks through an increase in assignment and validation requests. In particular, if a user can migrate from one subnet to another, the user's IP address that was valid in the user's prior subnet may be invalid in the user's new subnet. However, the user may determine that the IP address from the former subnet is valid within the new subnet by broadcasting an IP address validation request (validation request) to an IP address server that serves the new subnet. Similar to an assignment request, a validation request is also traditionally broadcast to all network hosts within a subnet, and is therefore broadcast to all users and IP address servers connected to the new subnet.
Traditional wireless network systems employ known communication techniques including TDMA and CDMA (e.g., cdma2000 or W-CDMA) to communicate information between a mobile terminal and the wireless network. The wireless network itself includes a plurality of base stations that are connected as a network by traditional network connection means (e.g., Ethernet), and the wireless network may also be connected to other wireless or wireline networks, as well as subdivided into smaller wireless network subnets. Base stations communicate with mobile terminals connected to the wireless network by transmitting information to the mobile terminals and receiving information from the mobile terminals over radio channels. Similarly, mobile terminals connected to the wireless network communicate with base stations by transmitting information to the base stations and receiving information from the base stations over radio channels.
Wireless IP networks operate in a similar fashion to traditional wireless networks, but they employ Internet Protocol to communicate information between the wireless IP network and mobile terminals. Thus, mobile terminals that employ Internet Protocol to communicate information are able to communicate with a wireless IP network. Such mobile terminals include any wireless device that communicates information using Internet Protocol or similar IP-based protocols, including mobile phones, Palm Pilots, pagers, personal media devices, personal computers with wireless IP-based access means, such as wireless Ethernet cards, and other similar devices. Base stations within the wireless IP network are themselves divided into subnets that include specific IP addresses, and these IP addresses form an address pool from which the subnet may allocate IP addresses to mobile terminals connected to the subnet.
When mobile terminals connect to the wireless IP network, they may need to dynamically acquire an IP address to communicate with the subnet as is required for traditional IP networks. Thus, upon establishing an initial non-IP-based communication link with the wireless IP network, a mobile terminal broadcasts an assignment request to the IP subnet for its particular wireless IP network connection. This assignment request is in turn broadcast to every network host within the mobile terminal's subnet, including IP address servers within the subnet, as well as all other mobile terminals within the subnet. After an IP address server receives the assignment request and assigns the mobile terminal a valid IP address, the mobile terminal will subsequently communicate with the IP network by unicasting messages only to the intended recipient using its own IP address which is valid for the subnet.
Similarly, when a mobile terminal migrates from its previous subnet to a new subnet, the mobile terminal must validate its IP address from the prior subnet as valid within the new subnet. Thus, the mobile terminal broadcasts a validation request to the new subnet, which is sent to all network hosts within the subnet including every other mobile terminal connected to the subnet. The validation request includes the IP address to be validated for the mobile terminal, and thus the validation request includes the IP address from the prior subnet. The destination IP address of the validation request is the broadcast IP address for the subnet. An IP address server that serves the subnet receives the broadcast validation request and responds by determining if the mobile terminal's former IP address from the prior subnet included in the validation request is valid within the new subnet. If the IP address from the former subnet is not valid, then the mobile terminal must request a valid IP address for the new subnet, as described above.
In the wireless IP network system described above, a number of problems are apparent in regard to traditional methods for assigning and validating IP addresses in wireless IP networks. First, each mobile terminal must broadcast an assignment request when initially connecting to a new IP subnet in the wireless IP network, and in particular, to the mobile terminal's subnet within the wireless IP network. As the assignment request is broadcast to every network host within the subnet including mobile terminals, base stations within the subnet unnecessarily transmit the assignment request to every mobile terminal within the subnet. Given the large number of mobile terminals that traditionally reside in a subnet, and the limited amount of wireless bandwidth for communications between mobile terminals and the wireless IP network, this broadcast of assignment requests to all mobile terminals reduces the amount of bandwidth available to communicate information, increases the latency of communications between mobile terminals and the wireless IP network, and causes an increase in transmissions and interference for mobile terminals and base stations. Also, the wireless broadcast of each assignment request to every mobile terminal reduces the number of mobile terminals the wireless IP network can support, causes the loss and non-delivery of IP data to base stations and mobile terminals, and may completely impair the wireless IP network due to loss of data and bandwidth. Even assuming a mere loss of bandwidth is the only tangible effect, there is still an increase in the cost to construct a wireless IP network because additional IP base stations are required to compensate for lost bandwidth and to communicate the same amount of information as if assignment requests were not being transmitted to mobile terminals.
A second problem is that mobile terminal validation requests are also broadcast to all mobile terminals within the IP subnet. Thus, even assuming that an IP address validation is broadcast by a mobile terminal and an IP address server verifies that the mobile terminal's current IP address is still valid, the validation request is nonetheless broadcast to every mobile terminal within the wireless IP network. Thus, validation requests further add to the information congestion, loss of bandwidth and increase of latency described above, along with the associated harmful side effects.
These problems are further aggravated by the fact that assignment and validation information returned by an IP address server is also broadcast to every mobile terminal when returning information to a requesting mobile terminal. Thus, the return broadcast by an IP address server is transmitted to every mobile terminal including those mobile terminals that have not requested assignment or validation information, and this return broadcast further diminishes the amount of wireless bandwidth available between the IP network base stations and mobile terminals.
In addition to the bandwidth reduction caused by assignment requests and validation requests, a third problem is that known protocols that accomplish dynamic IP address assignment, such as DHCP, do not notify a mobile terminal of when it should request a new IP address or validate its existing IP address. Thus, mobile terminals simply do not know when to request a new IP address or validate an IP address from a prior subnet when they migrate from one subnet to another. As a result, a mobile terminal may erroneously use an invalid IP address in a new subnet where the IP address is no longer valid, which will cause the mobile terminal to lose its ability to communicate with the wireless IP network.